This application claims the priority of German application 198 37 183.7, filed in Germany on Aug. 17, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an endless transport belt for transporting a drafted fiber strand though a fiber bundling zone, said transport belt comprising a perforation for an air suction stream which suctions the fiber strand as well as a sufficiently smooth surface on the inside for sliding over a suction device.
A transport belt of this type is prior art in US Pat. No. 5,600,872. It is produced in the way of a drafting apron of spinning machines, but more flexible, in that for example it has no woven insert. In addition, it is perforated for the purpose of suctioning the fiber strand, whereby the holes are arranged in one row in a fiber strand transport direction. The perforated apron slides over a suction device and is driven by means of a delivery roller.
It is an object of the present invention to produce a transport belt of the above mentioned type, which, with regard to the fiber bundling, is particularly favorably designed.
This object according to the present invention has been achieved in that in one embodiment the transport belt is a woven or knitted sieve belt, and in a second embodiment it is an extruded plastic apron with punched out holes.
The embodiment of the transport belt according to the present invention in the form of a woven or knitted sieve belt has the advantage in that on the one hand the perforations occur, so to speak, of their own accord, and on the other hand in that the perforations in transport direction are at absolutely identical distances from one another. The latter is very important for spinning a high quality yarn.
The sieve belt is advantageously produced from synthetic filaments, for example a polyamide. This has the advantage that the edges of the sieve belt can be welded. The diameter of the synthetic filaments should preferably measure less than 0.1 mm; the mesh width should also measure less than 0.1 mm. It has been shown that the more close-perforated the sieve belt is, the better the spinning results.
When the transport belt takes the form of an extruded plastic apron, it is necessary to punch out the holes. In order to reduce time and cost, a single row of holes suffices, which is adapted to the width of the fiber strand. The holes should have a diameter of approximately 0.6 to 1.0 mm.
When the extruded plastic apron is guided only on its inner side on a sliding guide and driven on its outer side, it is practical to provide two layers. The inner layer of the plastic apron should be particularly friction-free, so that the inner surface can slide efficiently over the suction device. PTFE is here an advantageous option. In contrast, the outer layer should be relatively stable in form, so that it can cope with the friction drive to be generated.